PICOSECOND TIME-RESOLVED FLUORESCENCE OF THE INTRAMOLECULAR EXCITED-STATE PROTON-TRANSFER IN 2-NAPHTHYL-3-HYDROXYCHROMONES - TORSIONAL RELAXATION IN THE EXCITED-STATES

The excited-state proton transfer (ESPT) and relaxation in 2-(1-naphthyl)- and 2-(2-naphthyl)-3-hydroxychromones (1- and 2-NHC) in 3-methylpentane (MP) were investigated by picosecond time-resolved fluorescence. Two components of tautomer fluorescence decay (almost-equal-to 700 and 4800 ps) were observed in 1-NHC, while only one-component decay (almost-equal-to 4900 ps) was detected in 2-NHC. The fluorescence decay features are consistent with the transient absorption and two-step laser-induced fluorescence of the ground-state tautomer reported previously. The results were discussed in terms of restricted torsional motion of naphthyl groups at the 2-position of these compounds.